The core layer copper thickness of conventional integrated circuit package substrates continues to increase as such substrates are required to route increasing amounts of power. A substrate may be electrically and physically coupled to a motherboard using an array of solder balls. The motherboard, in turn, tends to flex during shock and vibration thereof, platform assembly and testing. The above-mentioned increased thickness results in increased substrate rigidity that may prevent the substrate from flexing to accommodate the motherboard flexing. The flexing mismatch results in forces on the solder balls which may decrease their reliability.
Conventional techniques to address the foregoing include increasing a solder ball pad size on the substrate and on the motherboard. Other techniques include designing a substrate such that its corner solder balls, which tend to experience the greatest flexing forces, are sacrificial (i.e., not critical to electrical function). The former technique may increase a package footprint, and the latter technique reduces I/O density. Notwithstanding their effectiveness in addressing the above issues, the trade-offs presented by these techniques may unacceptable in any number of usage scenarios.